Those are great pics of the Pontiac cross ram intake. The top plate looks to be very similar to the Chevrolet item, I don't have one hand to compare them closely, does it look that way to anyone else ?
The other thing I notice is that the Pontiac cross ram intake ports are for the non Tunnel Port heads. No doubt they tried all the heads and manifold combinations , and it may well be that the smaller intake runners on the regular heads worked better than with the Tunnel Ports items.
Al Bartz has a fabricated intake on the engine he is looking over.
I have spoken to Dave Billes at Performance Engineering but he can't recall many specifics of the twin Dominator engines. Just another race engine.